Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5205896 | Polymer Testing | 2016 | 11 Pages |
Tension-tension fatigue behavior of a 2D unitized polymer/ceramic matrix composite and of a 2D polymer matrix composite (PMC) was studied at elevated temperature. The 2D PMC consisted of polyimide matrix reinforced with 15 plies of carbon fibers woven in an eight harness satin weave (8HSW). The unitized composite consists of a PMC co-cured with a ceramic matrix composite (CMC). The PMC part consisted of the polyimide matrix reinforced with 12 plies of an 8HSW carbon fiber fabric. The CMC part consisted of a zirconia-based ceramic matrix reinforced with 3 plies of an 8HSW quartz fiber fabric. In order to assess the performance and suitability of the two composites for use in aerospace components designed to contain high-temperature environments, mechanical tests were performed under temperature conditions simulating the actual operating conditions. In all elevated temperature tests performed in this work, one side of the test specimen was at 329 °C while the other side was open to ambient laboratory air. The tensile stress-strain behavior of the two composites was investigated and the tensile properties measured for both on-axis (0/90) and off-axis (±45) fiber orientations. Elevated temperature had little effect on the on-axis tensile properties of the two composites. The off-axis tensile strength of the PMC decreased slightly at elevated temperature, while the off-axis strength of the unitized PMC/CMC remained unchanged. Tension-tension fatigue tests were conducted at elevated temperature at a frequency of 1.0 Hz with a ratio of minimum stress to maximum stress of R = 0.05. Fatigue run-out was defined as 2 Ã 105 cycles. Both strain accumulation and modulus evolution during cycling were analyzed for each fatigue test. The PMC exhibited better fatigue resistance than the unitized composite. Specimens that achieved fatigue run-out were subjected to tensile tests to failure to characterize the retained tensile properties. Post-test examination under an optical microscope revealed severe delamination in both the PMC and the unitized PMC/CMC.